paolo ni



Nov 25; 1924.

A. PAOLONI ELECTRIC FURNACE Filed Feb. 8

I I A 3 Shanta-Sheet 1 Nov. 25, 1924- 1,517,122

A. PAOLONI ELECTRIC FURNACE FiledFeb. 8 1921 3 Shuts-Sheet. 2

Nov. 25, 4- 1,517,122

A. PAOLONI ELECTRIC FURNACE Filed Feb. 1921 3 Shasta-Sheet 3 Patented Nov. 25, 1924.

UNITED STATES PATENT OFFICE.

ARTURO PAOLONI, OF BADEN, SWITZERLAND, ASSIGNOR. BY MESNE ASSIGNMENTS, TO THE FIRMA MOTOR-COLUMBUS AKTIENGESELLSCHAFT FUR ELEKTRISCHE UNTEBNEHMUNGEN, OF BADEN, SWITZERLAND.

ELECTRIC FURNACE.

Application filed February 8, 1921.

To all whom it may concern:

Be it known that I, ARTURO PAOLONI, a subject of the King of Italy, residing at Baden, Switzerland, have invented certain new and useful Improvements in Electric Furnaces; and I do hereby declare the following to be a clear, full, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same, reference being had to the accompanying drawings, and to letters or figures of reference marked thereon, which form a part of this specification. I

This invention relates to improvements in electric furnaces.

The difliculty experienced heretofore in constructing an electric furnace workingon a large scale for baking refractory materials consisted mainly in obtaining inside the heating chamber which must necessarily be comparatively large and chargedwith these materials a very high temperature which is as nearly as possible uniform in all the parts of the heating chamber. Further it is of importance that the heating chamber is entirely independent of the electric current and the electrodes.

The object of the present invention is an electric furnace with a heating. chamber which chamber is characterized by the feature that it is separated from the electrodes and the electric current by at least one wall which is infusible and a good conductor of heat, opposite to which wall and at the outer side thereof the electric resistance (the socalled resistor) is arranged. The heat produced by the resistor is utilized for heating the chamber which heating is effected partly by the radiation of said wall and by con ducting the heat into the heating chamber by means of suitably shaped channels formed in this wall.

Several modes for carrying the invention into effect are shown by way of example in the accompanying drawings, in which:

Figs. 1 and 2 show a vertical and a horizontal section respectively through a first constructional example;

Figs. 3 and -l are vertical and horizontal sections through a second constructional example;

Fig. l is a vertical section through athird Serial No. 443,406.

constructional example illustrating a modification to the construction shown in Figs. 1 and 2;

Fig. 2 is a horizontal section through the furnace shown in Fig. 1,

Figs. 1 and 2 illustrate vertical and horizontal sections of a fourth constructional example.

Figs. 3* and 4 are vertical and horizontal sections through a fifth example which is a modification of the construction illustrated in Figs. 3 and 4. 7

Figs. 3 and 4 are corresponding sections through a'sixth example being a further modification of the construction shown in Figs. 3 and'4.

In the electric furnace illustrated in Figs. 1 and 2, the electric energy is transformed by means of the resistors, each of which consists of'a core 10 made of compressed carbon or ordinary carbon, the resistors being connectedto the electrodes 6 which are connected to the mains. The core 10 is surrounded by carbon or granulous graphite. In accordance with the J oule-efl'ect of the electric current the whole resistance is heated up to a maximum temperature of 2200 (1, lower temperatures may be obtained at will by regulating the tension. Each resistor is arranged in' between four side walls, two of which are opposite to each other, the electrodes-'6 passing through said Walls. The other twoside wallst) and 2 or 3 respectively are also opposite each other and consist of different material, the wall 9 serves for thermal insulation purposes, whereas the wall 2 or 3 respectively is a conductor of heat and is generally made of compressed carborundum combined with tar; The 'wal1s'2 and 3 form at the same time the walls of the heatingv chamber This material' can stand a temperature of 2000 C. without melting and without decomposing and its conductivity of heat is approximately four times as high as that of the best refractory brick, which brick moreover melts at a much lower temperature and is attacked by the glowing carbon of the resistor.

In order to obtain a maximum of heat transmission from the resistor to the heating chamber through the walls 2 and 3 the latter are provided with cavities or channels 4.

radiated IS in direct pmportion to the fourthower of the absolute temperature. Through the channels 4 theheat radiates directly into the heating. chamb'en 1; and". important calorific currents are thus produced whichflow into the-heatingchamben 1; Owing to the provision of said channels the calorific em ergy obtained by the transformatioirin the resistor of the electric energy into heat? according to the Joule-efiect, will preferably through the intermediate of these channels be conveyed into; the interior of-' the chain? ber.1;.

In all the cases in which it isintended to avoidthat thematerial ofs which the resistor is made iszexposed tothe chemical action of volatilegases es ecially of.- carbonic-acid dissociating from the roducts-tnbebaked, the channels 4: provi ed-in the heat conducting. walls: may be closed: by means-of thin diaphnagms 7, which: recent the'gases developed. from reaching. te resistor (Fig. 1" andi2?) i A furnace with a single chamber.- constructed on the aforementioned lines and heated by. two resistors connected in series is illustratdin-Figs 1 and.2. The channels 4 provided: in the walls-2 .and.-3-are .open at both-endsin this case and may, be-of eylindrical cross-section.. The upper part of the two resistors and the heating chamber are covered by refractory plates. The-cart bon or the granulated graphite of the re sistor. may also be covered. by. a layer of siliceous sand. If; the insulationaroundt the fumace is made properly the thermal efliciency is very high.

A similar furnace to that shown in Figs. 1 and 2 is illustrated in: Figs. 1 and 2, the distinguishing feature being that the channels 4 provided in the side walls 2 and 3 are closed a ainst the resistor by means of a diaphragm l. whilst the cross-sectional area of the channels increases towards the heating chamber 1. This" type of furnace may. be worked with single phase as well as with continuous current. i

Figs. 1" and 2" illustrate-a-constructional example of a furnace provided with three resistors for three phase current; whereby two chambers 1 are heated: the cmsssectional area of the channels 4 increases towards-the heating chamber, but there are no diaphragms providedatthe endsof the channels. It is evident-.thatafurnace could be constructed consisting 01 six resistors and five heating chambers l= and this arrangement; is the most-economical? In. the furnace illustrated in 2g.

4 a number ofpipes-S open at both ends am. the cross-section of which may be cyliir dricahareprovidedin eachresistor and lead into the heating chamber 1. These pipes Smay be made of compressed carbon or better of compressed graphite and are surroundedbythe carbon or ill: granulated graphite of the resistor and form a part of the resistoa The-pipes actin. the same manner as thechaimels described-above. The pipes could also-be constructed so that the cross-sectional areaincreascs towards the heating chamber 1. The pipes may also be closedattheir one end: by means of a thin diaphragmas is shown. in Figs. 3' and 4"; The constructional. example illus traficd. in these figures is built for single phase current and: is provided with: two resistors,'- in which. pipes 8 are arranged. which tenminate within the resistor with their closed ends;

Figs. 3" and 4" illustrate an armngement for a: furnace: for three phase current, in which the pipes 8 are closed-at. their one end bmeans of diaphragms 7 and are embedded: withthein' closedends in the resiston. The centre iesistor 5. is; however, prnvsidediwith es 8 open at.both ends-and terminating; into. oth chambers: 1..

The furnaces-described above iespond to all requirements; of; the ceramic industry with regard to furnaces. Objects of porcelainzmaybe subjected to a'firstz bakEngprocess at a-temp'erature of from 800 to 900 C. by. working. the resistorswith a lower 'tension and connecting a plurality of resistors in series. For the second halting period at a tempenrture'of from 1.400 to 1500 C. the tension is: incl-arsed and the X'ClilStK)l$ are connected in parallel.

Asthe heating chamber is entirely inde pendent of the electric current and of. the electrodes it? is-eas y to construct a. kiln of the t.unnel:t -'-pe for baking bricks. The objects to be, baketh such as limestone. glass, cement, magnesian limest'one magnesite,.refractony, earth and-bricks, clay-bricks, may be-charged either directly into the chamber 1 or into mufilesin which electrodes; objects of porcelain and the like may be treated. \Vitn a large mufile difl'erent chcn'iical and metallurgical processes maybe carried out amongst which also the processes fortreating solidobjects-atl ahightempemture with nitrogen. The furnaccsmay also serve for heatingiron-and steel blocks to a; high temperature or for other purposes in producing iron or steel.

Claims:

1. In an electric furnace having a heating1chainber, a resistor solely acting. as heat producer, an infusible, heat-conducting wall separating said resistor from a heating chamber and having channels therethrough, a thin diaphragm closing said channels towards the resistor to prevent circulation of gases between the resistor and the heating chamber and vice versa, thereby increasing the transmission of heat from the resistor to the chamber.

2. In an electric furnace having a heating chamber, a resistor solely acting as heat producer, an infusible heat-conducting wall separating said resistor from said heating chamber, and horizontally arranged pipes of refractory material, which pass at least partly through the resistor being provided in said walls for increasing the transmission of heat from the resistor to the chamber.

3. In an electric furnace having a heating chamber, a resistor solely acting as heat producer, an infusible heat-conducting wall separating said resistor from said heating chamber, and horizontally arranged pipes of refractory material, which pass at least partly through the resistor being provided in said walls for increasing the transmission of heat from the resistor to the chamber, and a thin diaphragm closing the end of each pipe towards the resistor to prevent circu- Iation of gases between the resistor and the heating chamber and vice versa.

4. In an electric furnace having a heating chamber, a resistor solely acting as heat producer, an infusible heat conducting wall separating said resistor from said heating chamber, and horizontally arranged pipes of carbonaceous material passing through said Walls for increasing the transmission of heat from the resistor to the chamber.

5. In an electric furnace having a heating chamber, a resistor solely acting as heat producer, an infusihle heat-conducting wall separating said resistor from said heating chamber, and horizontally arranged graphite pipes for increasing the transmission of heat from the resistor to the chamber.

In testimony that I claim the foregoing as my invention, I have signed my name.

ARTURO PAOLONI. 

